Habitat point records from 1978-79 SWBSS Upper Bristol Channel sublittoral survey

This survey was carried out to describe the range of sublittoral habitats and the communities of plants and animals present adjacent to the coast of the upper Bristol Channel. On the north side, from the east side of Swansea Bay to Llantwit Major and on the south side, at Porlock Bay, Minehead and Watchet. 16 sites were surveyed by diving within 43 km of coastline. All of the sites, except Gore Point on the west side of Porlock Bay, included a very small number of species of algae and animals compared to open coast areas of south-west Britain. Algae were only recorded above Chart Datum level. Animal communities were similar from site to site with stable rock surfaces at most sites dominated by Sabellaria spp. (mostly S. alveolata) and at some sites by Dendrodoa grossularia, Mytilus edulis or Polydora ciliata. A small variety of sponges, hydrozoans and bryozoans were also present in large amounts. Mobile or scoured substrata were characterised by Balanus crenatus and Pomatoceros triqueter. Moving west to east along the coast reveals a gradual reduction in the number of conspicuous species with a sharp reduction across Swansea Bay resulting in highly impoverished communities here. Along the majority of the coast studied, it is suggested that the circalittoral zone extended above the Chart Datum level and that the upward extent of the sublittoral zone, based on the presence of sublittoral algae, extended to about 2.5 m above Chart Datum compared to about 1 m on the open coast. The presence of extensive areas of sand and of sand in suspension during strong tidal flow, is considered to be important in the development of large colonies of Sabellaria alveolata. This and previous surveys emphasise the importance of S. alveolata as a dominant species. Records currently considered sensitive have been removed from this dataset.

本调查旨在描述上布里斯托尔海峡沿海地区的海底栖息地范围以及与之相邻的植物和动物群落。调查范围包括从斯旺西湾东侧至兰尼威特马杰尔，以及南边的波洛克湾、明赫斯特和沃切特。在距离海岸线43公里以内的区域内，共对16个地点进行了潜水调查。除波洛克湾西侧的戈尔角外，所有地点的藻类和动物物种数量相较于英国西南部开阔海岸地区而言极为有限。藻类仅记录在高于基准面水平之上。动物群落从一处到另一处相似，大多数地点的稳定岩石表面以管珊瑚属（主要为S. alveolata）为主，部分地点则以Dendrodoa grossularia、Mytilus edulis或Polydora ciliata为主。此外，大量的小型海绵、水螅动物和苔藓动物也存在于调查地点。活动性或冲刷性底质以Balanus crenatus和Pomatoceros triqueter为特征。沿着海岸从西向东移动，可以发现显眼物种数量的逐渐减少，尤其是在斯旺西湾的急剧减少，导致此处群落极为贫瘠。在研究的大多数海岸线上，推测环海底带延伸至基准面之上，并且基于海底藻类的存在，海底带向上延伸至基准面以上约2.5米，而开阔海岸地区则为约1米。在强潮汐流期间广泛存在的沙质区域和悬浮的沙粒，被认为对管珊瑚属S. alveolata大型群体的形成至关重要。本调查及之前的调查都强调了S. alveolata作为优势物种的重要性。目前认为敏感的记录已被从本数据集中移除。